Injection drug use (IDU) is a major risk factor for the transmission of hepatitis C virus (HCV) and HIV. Persons with HIV/HCV coinfection have an increased risk of death from end-stage liver disease compared to those with HCV alone, but reasons for the accelerated liver disease are unclear. In chronic HCV infection, cell-mediated immunity may induce liver disease while engaging in an ineffectual effort to combat the persistent viral infection. If this hypothesis is correct, then it is paradoxical that HIV infection, which results in an immunocompromised state, is associated with accelerated liver disease. This suggests a more complex mechanism in which the balance of type 1, type 2, and pro-inflammatory immune responses may be as relevant as the frequency of immune response associated with progressive liver disease. In order to define the immunopathology of HCV-related liver disease, it is important to understand common, potentially immunomodulatory co-factors such as substance use. However, surprisingly little is known about the contributions of drug use to altered cellular immune responses in humans. In preliminary data, we found that IDU shifts the phenotype of antigen-specific immune responses to a type 2/pro-inflammatory profile, with evidence of broad immune activation in HIV/HCV IDU. The goal of this proposal is to dissect immunological effects of opiates per se from effects of injected heroin. We will examine a natural history cohort of subjects with HCV or HIV/HCV coinfection and detailed substance use histories taken at time of PBMC collection. We will compare active heroin IDU to methadone users (neither of whom use cocaine or alcohol) and nonusers (no injection drugs, alcohol, cocaine or methadone). We will determine immune responses in each of these groups using ELISpot assays for IFN3, IL-2, IL-10 and TNF1 against HCV proteins, inactivated HIV-1, and recall antigens as well as a panel of other cytokines and chemokines potentially related to HCV immunopathogenesis. We will also culture PBMC from nonusers with morphine naloxone and measure immune responses in order to determine direct effects of opiates on antigen-specific immunity. If our hypothesis is true, then either all opiate use, or IDU in particular, must be taken into account when studying the immunopathogenesis of HCV-related liver disease. It will also provide strong rationale for determining whether broad immune activation, as seen in preliminary data for HIV/HCV IDU, is associated with accelerated HCV- related liver disease.Project Narrative [unreadable] [unreadable] Injection drug use fuels much of the epidemic of HIV and hepatitis C infection. The role of the immune system is critical for understanding diseases associated with HIV and HCV but the impact of IDU on immunity is poorly understood. This proposal will determine how opiate use affects HCV and HIV related cellular immune responses. [unreadable] [unreadable] [unreadable]